A vane pump is used as a hydraulic source that supplies working oil to a hydraulic apparatus such as a transmission, a power steering apparatus, and so forth mounted on a vehicle.
JP2001-248569A discloses a vane pump including a plurality of pump chambers that are partitioned by a plurality of vanes between a cam ring and a rotor, suction ports that guide the working oil to the pump chambers undergoing an expansion stroke, discharge ports to which the working oil discharged from the pump chambers undergoing a compression stroke is guided, and groove-like notches that guide the working oil discharged from the pump chambers commencing an initial stage of the compression stroke to the discharge ports.
The above-mentioned groove-like notches extend in the opposite direction from the rotation direction of the rotor from opening edges of the discharge ports. The notches each has a shape in which a groove depth and an opening width gradually increase from its distal-end portion towards proximal-end portion and has a part at which a rate of change of the groove depth gradually increases from the distal-end portion towards the proximal-end portion.